This invention relates generally to a temperature dectector circuit of the type used in small sized electronic timepieces for correction of inaccuracies in timekeeping and more particularly to a temperature detector circuit using intergrated resistors. This invention relates to a temperature detector circuit using the temperature sensitive characteristics of a resistor. Conventionally, such a thermo-sensitive device, for example, a thermistor, is used in a temperature detecting system which relies on the temperature characteristics of the resistor. In such a system there is the advantage that the sensitivity to temperature is very good because of the large temperature coefficient of that type of resistor. On the other hand, there is the disadvantage that such a thermo-sensitive element must be provided separate from an intergrated circuit as when such a circuit is used to compensate for temperature induced variations in a quartz crystal oscillator of a timepiece with a liquid crystal display.
It is conventional, in electronic timepieces to utilize a tuning-fork quartz crystal vibrator operating in a flexural mode and having a resonant frequency of 32.678 KHz. Such a tuning-fork type vibrator is widely used especially in watches because this vibrator can easily be manufactured in small size which is suitable to a timepiece for the wrist. However, a tuning-fork type quartz crystal vibrator has deficiencies in that the temperature characteristic is poor and changes in oscillating frequency due to aging are significant. In order to overcome these deficiencies, a titanic acid barium condenser which has a similar temperature characteristic to the quartz cyrstal vibrator, or two quartz crystal vibrators are used together so as to meet the desired timekeeping accuracy specification.
Unfortunately, these methods require too many steps in compensation and require that the titanic acid barium condenser or the supplemental quartz crystal be very narrowly specified for suitable performance. Also these elements need to be set outside of the intergrated circuit of the timepiece such that production efficiency is significantly reduced and costs are increased. Further, the number of components which are set apart from the intergrated circuit is a factor which prevents a timepiece from being made in a small size and with a good appearance design.
What is needed is a temperature detector circuit for a timepiece which is highly sensitive in performance and is formed as part of the intergrated circuitry associated with the timepiece and requires no externally attached components.